Add JS linting config and lint JS files

Add basic eslint config, including project-wide lint settings in the root
of the docs/ dir, as well as browser-and-js-vendor-specific lint config
under assets/js, and finally testing-specific lint config under spec/.

Set to ignore the generated _site dir and the assets/js/vendor dir

Author: filmaj

docs/.eslintignore

@@ -0,0 +1,2 @@
+_site/**
+assets/js/vendor/*.js

docs/.eslintrc.json

@@ -0,0 +1,24 @@
+{
+    "parserOptions": {
+        "ecmaVersion": 6
+    },
+    "extends": "eslint:recommended",
+    "rules": {
+        "brace-style": ["error", "allman", {"allowSingleLine": true}],
+        "camelcase": ["error"],
+        "comma-spacing": ["error", {"before": false, "after": true}],
+        "indent": ["error", 4, {"SwitchCase": 1}],
+        "key-spacing": ["error", {"beforeColon": false, "afterColon": true}],
+        "keyword-spacing": ["error", {"before": true, "after": true}],
+        "max-len": ["error", {"code": 116}],
+        "object-curly-spacing": ["error", "never"],
+        "no-case-declarations": ["off"],
+        "no-tabs": ["error"],
+        "no-trailing-spaces": ["error"],
+        "no-var": ["error"],
+        "quotes": ["error", "single"],
+        "semi": ["error", "always"],
+        "space-before-function-paren": ["error", "never"],
+        "space-in-parens": ["error", "never"]
+    }
+}

docs/README.md

@@ -32,11 +32,29 @@ as the testing / assertion library. The tests are implemented as `.js` files und
 
 ### Running the Tests
 
-To run the tests once:
+To run the tests and linter:
 
     $ npm test
 
+To run just the unit tests once:
+
+    $ npm run unit-test
+
 During local development, it may be nice to keep the test runner running in the background as one makes changes to the JavaScript source files (under `assets/js/`), or the test files (under `spec/`) so as to
 get immediate feedback. This mode will re-run the tests every time a source or test file changes. To run in this mode:
 
-    $ npm test -- --no-single-run --auto-watch
+    $ npm run unit-test -- --no-single-run --auto-watch
+
+#### Linting JavaScript
+
+This project has formalized a JS style using the [ESLint tool](https://eslint.org). To run the linter, ensure you have dependencies installed via `npm install`, then run:
+
+    $ npm run lint
+
+ESLint allows for [cascading rules](https://eslint.org/docs/user-guide/configuring#configuration-cascading-and-hierarchy) to be in place, which this project leverages:
+
+- There is one "global" ESLint config defined in [`.eslintrc.json`](.eslintrc.json), where we house the main stylistic rules.
+- We also have a browser-context-specific config defined in [`assets/js/.eslintrc.json`](assets/js/.eslintrc.json).
+- Finally, we have a test-context-specific config defined in [`spec/.eslintrc.json`](spec/.eslintrc.json).
+
+The [`.eslintignore` file](.eslintignore) defines what directories and files we should not lint.

docs/assets/js/.eslintrc.json

@@ -0,0 +1,14 @@
+{
+    "parserOptions": {
+        "ecmaVersion": 6
+    },
+    "env": {
+        "browser": true,
+        "jquery": true
+    },
+    "globals": {
+        "Chart": false,
+        "d3": false,
+        "Spinner": false
+    }
+}